/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file KnownState.h
* @author Christian <c@ethdev.com>
* @date 2015
* Contains knowledge about the state of the virtual machine at a specific instruction.
*/
#pragma once
#include <vector>
#include <map>
#include <set>
#include <tuple>
#include <memory>
#include <ostream>
#pragma warning(push)
#pragma GCC diagnostic push
#pragma clang diagnostic ignored "-Wredeclared-class-member"
#include <boost/bimap.hpp>
#pragma warning(pop)
#pragma GCC diagnostic pop
#include <libdevcore/CommonIO.h>
#include <libdevcore/Exceptions.h>
#include <libevmasm/ExpressionClasses.h>
#include <libevmasm/SemanticInformation.h>
namespace dev
{
namespace eth
{
class AssemblyItem;
using AssemblyItems = std::vector<AssemblyItem>;
/**
* Class to infer and store knowledge about the state of the virtual machine at a specific
* instruction.
*
* The general workings are that for each assembly item that is fed, an equivalence class is
* derived from the operation and the equivalence class of its arguments. DUPi, SWAPi and some
* arithmetic instructions are used to infer equivalences while these classes are determined.
*/
class KnownState
{
public:
using Id = ExpressionClasses::Id;
struct StoreOperation
{
enum Target { Invalid, Memory, Storage };
StoreOperation(): target(Invalid), sequenceNumber(-1) {}
StoreOperation(
Target _target,
Id _slot,
unsigned _sequenceNumber,
Id _expression
): target(_target), slot(_slot), sequenceNumber(_sequenceNumber), expression(_expression) {}
bool isValid() const { return target != Invalid; }
Target target;
Id slot;
unsigned sequenceNumber;
Id expression;
};
explicit KnownState(
std::shared_ptr<ExpressionClasses> _expressionClasses = std::make_shared<ExpressionClasses>()
): m_expressionClasses(_expressionClasses)
{
}
/// Streams debugging information to @a _out.
std::ostream& stream(std::ostream& _out) const;
/// Feeds the item into the system for analysis.
/// @returns a possible store operation
StoreOperation feedItem(AssemblyItem const& _item, bool _copyItem = false);
/// Resets any knowledge about storage.
void resetStorage() { m_storageContent.clear(); }
/// Resets any knowledge about storage.
void resetMemory() { m_memoryContent.clear(); }
/// Resets any knowledge about the current stack.
void resetStack() { m_stackElements.clear(); m_stackHeight = 0; }
/// Resets any knowledge.
void reset() { resetStorage(); resetMemory(); resetStack(); }
unsigned sequenceNumber() const { return m_sequenceNumber; }
/// Replaces the state by the intersection with _other, i.e. only equal knowledge is retained.
/// If the stack heighht is different, the smaller one is used and the stack is compared
/// relatively.
/// @param _combineSequenceNumbers if true, sets the sequence number to the maximum of both
void reduceToCommonKnowledge(KnownState const& _other, bool _combineSequenceNumbers);
/// @returns a shared pointer to a copy of this state.
std::shared_ptr<KnownState> copy() const { return std::make_shared<KnownState>(*this); }
/// @returns true if the knowledge about the state of both objects is (known to be) equal.
bool operator==(KnownState const& _other) const;
/// Retrieves the current equivalence class fo the given stack element (or generates a new
/// one if it does not exist yet).
Id stackElement(int _stackHeight, SourceLocation const& _location);
/// @returns the stackElement relative to the current stack height.
Id relativeStackElement(int _stackOffset, SourceLocation const& _location = SourceLocation());
/// @returns its set of tags if the given expression class is a known tag union; returns a set
/// containing the tag if it is a PushTag expression and the empty set otherwise.
std::set<u256> tagsInExpression(Id _expressionId);
/// During analysis, different tags on the stack are partially treated as the same class.
/// This removes such classes not to confuse later analyzers.
void clearTagUnions();
int stackHeight() const { return m_stackHeight; }
std::map<int, Id> const& stackElements() const { return m_stackElements; }
ExpressionClasses& expressionClasses() const { return *m_expressionClasses; }
std::map<Id, Id> const& storageContent() const { return m_storageContent; }
private:
/// Assigns a new equivalence class to the next sequence number of the given stack element.
void setStackElement(int _stackHeight, Id _class);
/// Swaps the given stack elements in their next sequence number.
void swapStackElements(int _stackHeightA, int _stackHeightB, SourceLocation const& _location);
/// Increments the sequence number, deletes all storage information that might be overwritten
/// and stores the new value at the given slot.
/// @returns the store operation, which might be invalid if storage was not modified
StoreOperation storeInStorage(Id _slot, Id _value, SourceLocation const& _location);
/// Retrieves the current value at the given slot in storage or creates a new special sload class.
Id loadFromStorage(Id _slot, SourceLocation const& _location);
/// Increments the sequence number, deletes all memory information that might be overwritten
/// and stores the new value at the given slot.
/// @returns the store operation, which might be invalid if memory was not modified
StoreOperation storeInMemory(Id _slot, Id _value, SourceLocation const& _location);
/// Retrieves the current value at the given slot in memory or creates a new special mload class.
Id loadFromMemory(Id _slot, SourceLocation const& _location);
/// Finds or creates a new expression that applies the Keccak-256 hash function to the contents in memory.
Id applyKeccak256(Id _start, Id _length, SourceLocation const& _location);
/// @returns a new or already used Id representing the given set of tags.
Id tagUnion(std::set<u256> _tags);
/// Current stack height, can be negative.
int m_stackHeight = 0;
/// Current stack layout, mapping stack height -> equivalence class
std::map<int, Id> m_stackElements;
/// Current sequence number, this is incremented with each modification to storage or memory.
unsigned m_sequenceNumber = 1;
/// Knowledge about storage content.
std::map<Id, Id> m_storageContent;
/// Knowledge about memory content. Keys are memory addresses, note that the values overlap
/// and are not contained here if they are not completely known.
std::map<Id, Id> m_memoryContent;
/// Keeps record of all Keccak-256 hashes that are computed.
std::map<std::vector<Id>, Id> m_knownKeccak256Hashes;
/// Structure containing the classes of equivalent expressions.
std::shared_ptr<ExpressionClasses> m_expressionClasses;
/// Container for unions of tags stored on the stack.
boost::bimap<Id, std::set<u256>> m_tagUnions;
};
}
}
